Re: Rotary engines

Erik Pilawskii (
Wed, 7 Dec 1994 14:25:30 -0800 (PST)

> John,
> The rotary engine was developed as a light weight alternative to the water
> cooled automobile engines then in use. By spining the motor it was possible
> to air cool a high horse power engine and prevent engine failure due to poor
> iginition timing ( the fly wheel action would carry the motor over rough spots
> and the cooling would allow higher combustion temperatures).
> Although the conventional radial engine as we know it today was in
> development, because of over heating and pre-detonation it was notoriously
> unreliable and wasn't really prefected until the 1920's. The simple turth of
> the matter was, despite all it's short commings the the rotary was the most
> compact, highest power to weight ratio aero engine availble for the major part
> of WWI. Advances in motor consrtuction would allow the development of more
> powerful liquid cooled inline motors as the war progressed but the rotary was
> still lighter and simpler to operate and maintain in the field.
> And like its later radial bother the air cooled engine was less prone to being
> put out of action due to battle damage. The reams of tubing and exposed
> raditors meant that water cooled engine just presented more possible places for
> the engine to be disabled.
> Tally ho
> Guy
Good stuff. Might I add the following:
Rotaries were lighter in weight primarily because they were much less
complicated in construction. They had no long, heavy, finely balanced
crankshaft; no reduction gearing (typically-- there were exceptions);no
radiators or coolant jackets; no distributors.
Furthermore, they were painfully easy to replace-- a good mechanic was
said to be able to affect an engine change in 90 min, or less! Try that
on a Mercedes in-line six! Early liquid-cooled motors were prone to
serious vibration (ie. Hispano V-8), blown gaskets, and carburetion
difficulties of every kind. None of these apply to rotaries. Being
lubricated with castor oil they suffered from no clogged or frozen oil pumps
or pipes (though it must'ev made the pilot's life a treat! I sometimes wonder
if all that clothing they wore was *entirely* due to cold!!), and probably
fouled their spark-plugs much less frequently (predetonation and oil-fouling
being the primary plug killers). Some rotaries lacked plugs altogether.
You can imagine the stupendous difference in maintenance.

Just for Interest's Sake, Erik
"The Heavens were the grandstands, and only the Gods were spectators. The
stake was the World. The forfeit was the Player's place at the table; and
the Game had no recess. It was the most dangerous of all sports-- and the
most fascinating. It got in the blood like wine. It aged men 40 years in
40 days; it ruined nervous systems in an hour. It was a fast game-- the
average life of a pilot at the Front was 48 hours. And, to many, it
seemed an Age....
Elliot White Springs, WWI ace